Winter temperatures can lead to power loss in diesel engines, which can be frustrating and potentially dangerous. Diesel fuel treatments provide an additional level of security against these problems and can restore performance and ensure filters do not clog.

Wax and water are the sources of problems

Paraffin wax, a natural element in diesel fuel, contributes to its energy content. However, when temperatures drop, wax crystals form and cling to one another. As temperatures continue to decrease, formation continues until it restricts the flow of fuel through fuel filters, eventually stalling the engine. This wax formation in fuel is commonly known as “gelling.” Cloud point and pour point are two other terms that come up in conversation about winter diesel fuel. The following are the highlights of each:

Cloud point and cold-filter-plugging point (cloudy and clogged)

Cloud point is the temperature at which paraffin forms cloudy wax crystals

Cold-filter-plugging point (CFPP) is the point at which the crystals clog the fuel filter

Depending on the source of the #2 diesel fuel, the cloud point may be as high as 40°F (4.4°C)

The cold-filter-plugging point is slightly lower than the cloud point, which could be near freezing (32ºF), depending on the fuel source

#1 diesel fuel contains less wax and has cloud and pour points of typically -20°F or colder

Pour point (stops flowing)

Pour point is the temperature at which the paraffin in the fuel has crystallized so severely that the fuel resists flowing (pouring)

Depending on the fuel source, the pour point typically falls between 10°F (5.6°C) to 20°F (11.1°C) below the cloud point

Water contamination can also result in problems when freezing temperatures cause any emulsified (mixed) water to form a fuel/ice slush, which can also restrict filters. Proper storage-tank and filtration maintenance eliminate water-related issues.

Preventing diesel problems

Blending #1 & #2 diesel fuel

Blending #1 diesel fuel with #2 fuel lowers the wax level and the corresponding cloud, cold-filter-plugging and pour points. The more #1 added, the better the cold-temperature performance. Most fuel stations begin blending diesel fuel in the fall and continue through the winter. While #1 diesel fuel has an advantage due to its lower wax content and cloud point, the energy content of #1 diesel fuel is about five percent less than #2 diesel fuel, resulting in reduced fuel economy and less horsepower. In addition, #1 is also more expensive than #2 diesel. Although fuel stations work to ensure their blends cover historical temperature trends, temperatures can shift and gelling can still occur.

Additional security for your fuel

Adding a winter fuel additive to diesel fuel provides an additional level of protection against shifts in temperature and the corresponding expenses and hassles of cold-filter plugging.

Changing the temperature at which wax forms can be accomplished with chemical technology called “cold-flow improvers.” It is very common for your fuel station to have winter-blended fuels that use this technique to improve the cold-weather operability of the diesel fuel they sell.

In the fuel industry there is a test called the Cold-Filter-Plugging-Point Test. It measures the coldest temperature at which fuel will flow without plugging a filter.

In independent testing, AMSOIL Diesel All-In-One repeatedly flowed at temperatures up to 32ºF colder than Howes Lubricator Diesel Treat*. That is a substantial difference in performance when it matters most.

Diesel fuel additives that prevent gelling must be used at temperatures above the cloud point, and the same holds true for #1 diesel. Once filters become clogged or the fuel gells, adding #1 fuel or additives that prevent wax from forming will not remove the crystals that have already formed, and filters will remain clogged.

If it’s gelled, now what?

Clogged filters and gelled fuel pose a serious problem, particularly for professional truck drivers and fleets. Removing fuel and filters and replacing them with properly treated fuel can be costly. In the competitive world of transportation, delays and towing charges can eat into profits and reputations.

AMSOIL Diesel Recovery quickly dissolves gelled fuel to allow the operator to continue driving with minimal downtime. AMSOIL Diesel Recovery separates the molecular bonds of wax crystals that have agglomerated in diesel fuel. It thaws frozen fuel filters and reduces the need for a new filter, saving money and preventing an inconvenient trip to an auto parts store.

*Based on independent testing in July 2017 of AMSOIL Diesel All-in-One and Howes Lubricator Diesel Treat using diesel fuel representative of the U.S. marketplace and Howes’ recommended treat ratio for above 0°F.